// write your code here cpp
#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	long a[21] = { 0,0,1 };
	long b[21] = { 1,1,2 };
	for (int i = 3;i <= 20;i++)
	{
		a[i] = (i - 1) * (a[i - 1] + a[i - 2]);
		b[i] = b[i - 1] * i;
	}
	int n;
	while (cin >> n)
	{
		printf("%.2f%\n", 100.0 * a[n] / b[n]);
	}
	return 0;
}